A collage of methane sources
Credit: Jenessa Duncombe, Unsplash/Joel Vodell/Hans Ripa/Bakhrom Tursunov/American Public Power Association/Ryan Christodoulou, NASA/NASA’s Earth Observatory/ NASA’s Scientific Visualization Studio Data Visualization of Permafrost Status, Data: NOAA Global Monitoring Laboratory

A basic fact about climate change is curiously absent from public consciousness.

One reason: It holds a riddle that scientists don’t yet understand.

Methane, a potent greenhouse gas, has been rising in the atmosphere at an accelerating rate since 2007. But the cause of the acceleration remains unknown.

Today, NOAA announced more sobering news. In 2021, methane rose more than other any other year on record, according to a preliminary analysis of weekly measurements taken at 40 sites globally. 2020 also broke records.

It’s rare to feel like climate change is a mystery anymore.

Academic journals whirl with theories of methane’s rise. Conference sessions unravel into brainstorming. One group of academics has taken the extraordinary step of sending surveys to ask other researchers their opinion on the matter.

It’s rare to feel like climate change is a mystery anymore. When the Intergovernmental Panel on Climate Change (IPCC) formed, controversy besieged even basic facts: Is the planet warming? Are sea levels rising?

Those squabbles have long since ebbed, and political logjams have risen in their place. While lawmakers debate, people suffer and lose their lives from heat and storms worsened by climate change. With so much at stake, there’s a heightening sense that the science is settled. Science historian Naomi Oreskes called for the end of the IPCC’s deliberations on the physical science of climate change, arguing that all efforts must instead go toward finding solutions.

But when it comes to methane, the science is not settled. And that matters.

When it comes to methane, the science is not settled. And that matters.

Methane is one of the most powerful levers to quickly stop warming. According to the IPCC’s latest report, meeting the goals of the Paris Agreement is impossible without cutting methane emissions by one third this decade.

The good news is that we know where to start. A large portion of methane emissions from oil and gas could be slashed with existing, low-cost technology, according to the IPCC and others. Many industry heavy hitters say they’re on board with the plan.

But there’s a fear from scientists that even if we cut emissions from fossil fuels, methane in the atmosphere will continue to grow. Higher emissions may be coming from natural swamps, bogs, and marshes, and anthropogenic emissions from livestock and landfills are likely growing as well. Thawing permafrost from the North looms large, too.

“It’s a very scary and serious situation,” said Ben Poulter, a climate scientist at NASA who has studied methane in the atmosphere for over a decade.

The curve of methane concentration in the atmosphere is a source of unending curiosity—and alarm—for scientists. Credit: Jenessa Duncombe, Data: NOAA Global Monitoring Laboratory. Click image for larger version.

I’m writing this series, The Curve, to chart the mysterious rise of methane in our atmosphere and to document researchers’ quest to find its source.

I first learned about the puzzle of rising methane last year. Since then, I’ve traveled with scientists who are searching for answers at the doorstep of the Arctic to the tropical mangroves of the Gulf Coast. Along the way, researcher after researcher described the methane curve—one even drawing it in the air with her fingers, a shape she knows from memory.

We now have one more data point to add: Methane rose 16.99 parts per billion last year. The year before, it increased by 15.27 parts per billion, which was the previous record holder since measurements began in 1983. The 2021 value is still being vetted by scientists and may drop slightly when the official number is released later this year.

There is a lesson we can learn from this riddle.

But this story is bigger than methane. As policymakers implement carbon-cutting technology on a scale and pace never seen before, I think there is a lesson we can learn from this riddle: Climate action can include more research, debate, and room to be wrong.

An early chapter of our climate story was illustrated by the dramatic upward curve of carbon dioxide over time. The Keeling curve became one of the most famous (or infamous) pieces of climate imagery on Earth.

In our next chapter, I expect methane, and its curve, will step into the spotlight.

—Jenessa Duncombe (@jrdscience), Staff Writer

Citation: Duncombe, J. (2022), A climate mystery warns us to heed the unknown, Eos, 103, https://doi.org/10.1029/2022EO220207. Published on 7 April 2022.
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